1. Field of the Invention
This invention relates to a cam apparatus for converting continuous rotational motions at a constant speed transmitted from driving sources such as a motor to the input shaft into rotational motions of the output shaft such as intermittent indexing and swing through the cam mechanism, and a pick and place apparatus in which the former is used.
2. Description of the Related Art
So far various types of cam apparatus have been proposed for converting continuous rotational motions at a constant speed transmitted from the driving source such as a motor to the input shaft into rotational motions of a specific pattern such as intermittent indexing through the cam mechanism. Among them, the Japanese Patent Application Laid Open No. 1997-297145 and others disclose cam apparatuses capable of converting the continuous rotational motion at a constant speed of an input shaft and outputting different rotational motions on two output shafts provided on the same shaft.
A sectional side elevation of this cam apparatus is shown in FIG. 12A and a sectional plan view is shown in FIG. 12B.
As illustrated in these plans, an input shaft 117 is rotatably supported on a housing 112 of this cam apparatus 111, and this input shaft 117 continuously rotates at a constant speed being driven by a driving source not shown. On this input shaft 117, a globoidal cam 113 for driving continuous rotation (referred to hereinafter as “cam for driving continuous rotation”) and a globoidal cam 115 for driving oscillating rotation (referred to hereinafter as “cam for driving oscillating rotation”) are provided jointly in the axial direction. Then, the cam for driving continuous rotation 113 is engaged with a turret 119, causes an output shaft for continuous rotation 121 above to rotate continuously, and further the cam for driving oscillating rotation 115 is engaged with a turret 123 and causes the output shaft for oscillating rotation 125 above thereof to rotate oscillating.
On the outside of this output shaft for oscillating rotation 125, a rotating table 127 is provided on the same shaft through a bearing. On this rotating table 127, an input gear 127a is fixed coaxially. This input gear 127a is engaged with an output gear 121a fixed coaxially on the output shaft for continuous rotation 121, and the continuous rotation of the output shaft for continuous rotation 121 is transmitted to the rotating, table 127 (this is also considered as an output shaft, and shall be referred to hereinafter as “output shaft 127”).
By such a configuration, the two output shafts 125 and 127 provided on the same shaft are given the task of performing mutually different rotational motions (oscillating rotational motion and continuous rotational motion for the cam apparatus 111). Further, on this cam apparatus 111, by adequately setting the cam curve of the cam for driving continuous rotation 113 and the cam for driving oscillating rotation 115, the continuous rotational motion at a constant speed of the input shaft can be converted—and two output shafts aligned on the same shaft can be given the tasks of performing desired rotational motions.
On the cam apparatus 111, however, the rotational motions of the two output shafts 125 and 127 are mutually independent, and these rotational motions cannot be composed into one motion and outputted. Therefore, when the output shaft is caused to perform a compound rotational motion such that the other output shaft is relatively rotated on the basis of the rotational motion, the cam curve becomes so complex that the work of designing the same becomes extremely difficult, requires a high designing capacity and the designing takes a long period of time.